536 STRATIGRAPHICAL GEOLOGY. 



cliff, facing westward, nearly three miles west of North Weare station, and 

 near the union of Dudley brook with a large tributary from the north- 

 west. Half a mile south from the cliff is a gneiss of this age, yellowish 

 from superficial oxidation of iron, having the strike N. 23° E., and a 

 vertical position. Other ledges occur a mile west, and at the town line 

 between Weare and Deering the dip is 85° N. 75° W. The next gneisses 

 crop out at J. Downing's, and in the brook to the east of his house, south- 

 east from Deering centre, and are thought to dip westerly. At D. Gregg's, 

 two miles south of Deering, is the unmistakable gneiss of the Lake 

 group, dipping 85° N. 70° W. This is upon a hill. The rock may not 

 be more than a mile in width. Ledges are rare in this neighborhood, 

 because of the extensive development of the lenticular hills of drift, to be 

 described fully hereafter. 



Next we have the larger portion of this area in Crotched mountain, in 

 Francestown. I have not ascended the summit of this peak, but on the 

 north and south sides ledges of Lake gneiss occur, which make it proba- 

 ble that the mountain is composed of the same. The large boulders on 

 the south side of the mountain are also of the same character, as would 

 be the case if our view is correct. About a mile and a half west of 

 Francestown village are the first known ledges of this rock, and they 

 occur through the township on the old turnpike leading to Hillsborough. 

 Near the town line the strata dip 80° N. 60° W. There are no ledges 

 exposed along the road on the south side of Crotched mountain, only 

 enormous boulders. The first rocks seen to the south-west of this moun- 

 tain are the overlying ferruginous schists, and the range just described is 

 therefore terminated. 



The Dunbarton-Pctcrborotigh Range. The next line of elevation is less 

 extensive. Nothing is seen of it, — that is, of this rock, — beyond the Dun- 

 barton elevation. It will be noticed that the five hundred feet contour 

 line almost isolates Dunbarton, and that the rock is largely the Lake 

 gneiss at the north-east end of this range. Moraines cover the low neck 

 of land connecting the Dunbarton island with Hopkinton, so that the 

 north-western limits of this rock are not fully known. To the north-east 

 it is easily confounded with the Concord granite. I think it well to say 

 that the latter stop with the south-west end of Great Turkey pond, and 

 hence the similar rock in the very south-west corner of Concord may 



